Cleaning and preserving of metallic surfaces



252. COMPOSITIONS,

Patented June 2, 1931 UNITED STATES PATENT OFFICE DEAL H. TOMPKINS, OFNITRO, WEST VIRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIESCOMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO CLEANING AND PRIESERVINGOF METALLIC SURFACES No Drawing.

The present invention relates to the cleaning and preservation ofmetallic surfaces, wherein the metal is in contact with a liquid of anacid nature. More particularly, the invention relates to the preventionof excessive pitting and embrittlement of a metal when subjected to anacid treating or pickling process.

Certain obj ects of the invention are to prevent the acid pickle liquorfrom attacking clean portions of the surface of a metal; to obviateover-pickling, embrittlement and pitting of the articles treated; tominimize the amount of metal lost in pickling; to increase theefficiency of the pickling operation and to prolong the effective lifeof the pickling bath and particularly to facilitate the picklingoperation. Other and further objects of the invention will be apparentfrom the following description and accompanying examples.

In the art of pickling, the metal to be cleaned is treated with a diluteacid to remove oxides such as rust, scale, and other deposits, afterwhich the metal is preferably washed with water and dipped into analkaline bath to remove the last traces of free acid. The acid removesthe rust and scale, but unfortunately, from the pickling standpoint,unless some agent to prevent such action is prescut, it attacks thecleaned metal itself, thereby causing loss of metal and producing anevolution of hydrogen gas, which escapes into the air, carrying with ita fine spray of the acid liquor from the bath and producing anatmosphere possessing corrosive prop: cities and one which is highlyinjurious to health.

By the present invention, these objectionable features of the picklingprocess are substantially overcome or reduced to a minimum. Toaccomplish the objects set forth in accordance with the presentinvention, there is added to the pickling bath a regulating agent oringredient which acts to re- Application filed October 11, 1930. SerialNo. 488,196.

strain the action of the acid from attacking clean metal but assists inremoving the rust, scale and other deposits, or in other words causesthe acid selectively to remove such materials without appreciablyattacking the clean portions of the metal.

The pickle regulator or inhibitor, as disclosed in the presentapplication, comprises a phosphoric acid derivative of reaction productof s'uifurdioxide" and an" aldehyde amine reaction product and"preferably a phosphoric "acid "derivative of a reaction product ofsulfur dioxide and an aldehyde derivative of a Schiffs base; that is, aproduct formed by reacting an aldehyde with a Schifls base, addingsulfur dioxide thereto and treating the product so formed withphosphoric acid of any concentration necessary to produce chemicalcombination at the reaction temperature employed. The productshereinafter described and employable in the manner set forth arelikewise useful in the cleaning of metals by immersion in or treatmentwith dilute solutions of non-oxidizing acids.

In the examples hereinafter set forth for carrying out the metalpickling process, conditions were imposed which duplicated, so far aspossible, those commonly followed in commercial practice, so far asconcerned acid concentrations and temperatures commonly employed.

Test pieces of steel approximately 4 x 3" in dimensions and known as 30gauge low carbon hot rolled sheets, were immersed in approximately 640cc. of a water solution of sulfuric acid containing approximately 6% byweight of 66 Be. acid to which had been added a small quantity of one ofthe preferred type of inhibitors. The loss in weight of the steel testpieces resulting from maintaining the strips in the pickle bath in themanner described for a definite period of time was then determined. Thetemperature of the pickling bath was maintained at from 176 to 185 F.(80 to 85 For the acid concentration set forth, commercial practice isto pickle at approximately 150 to 190 F. (66 to 88 C.). The results soobtained were compared with similar tests wherein the steel pieces weresubjected, under the conditions set forth, to the action of an acidsolution of the strength and for the time specified above, butcontaining no inhibitor.

One method whereby one of the preferred class of compounds, for examplea phosphoric acid derivative of the reaction product of sulfur dioxideand an aldehyde derivative of a Schiifs base, was prepared follows:

Substantially one molecular proportion of the product formed from thereaction of substantially three molecular proportions of acetaldehydeand substantially two molecular proportions of aniline, according to themethod set forth in U. S. Patent No. 1.659,152 granted to Clayton OlinNorth, was dissolved in an organic solvent, for example, a quantity ofacetone equal to one-third of the weight of the aldehyde-amine product.Substantially one-half a molecular proportion of sulfur dioxide waspassed thereinto at a rate slow enough for complete absorption andcombination to take place while agitating and maintaining a temperatureof approximately 30 to 60 C. To the product thus formed, substantiallyone molecular proportion of phosphoric acid, preferably having an acidstrength of approximately 85%, was added at a temperature ofsubstantially 50 to 7 0 C. After'the addition of the phosphoric acid wascompleted, the water present and the solvent employed, for exampleacetone, were removed preferably by evaporation. The product prepared inthe manner described, aftercooling,was a brittle resin,which formed afine powder when ground that was readily soluble in a pickle li uor, asfor example dilute sulfuric acid. sample of the material prepared asdescribed above was incorporated in a pickling bath in the mannerhereinbefore described. Thus a steel test piece 3" x 4", 30 gauge lowcarbon hot rolled sheets, exposing 24 square inches of surface andweighing 18.770 grams, was found to lose but 0.298 grams after 40minutes pickling in a 6% sulfuric acid solution containing 0.06 grams ofthe inhibiting product just described. A similar test piece weighing17.928 grams and treated in the same manner. but without the use of anyinhibitor, lost 7.165 grams. Thus, when the phosphoric acid derivativeof the reaction product of sulfur dioxide and the product formed byreacting substantially three molecular proportions of aoetaldehyde andsubstantially two molecular proportions of aniline is employed as aninhibitor, the loss in weight per square inch of surface exposedcorresponds to 0.0124 grams, whereas when no inhibitor is used the lossper square inch of surface exposed corresponds to 0.2985 grams. Fromthese results it is apparent that the metal loss resulting by picklingin dilute sulfuric acid solution containing the inhibitor specified isonly 4% as great as the loss resulting by ickling without the use of anyinhibitor. K greater saving in metal losses results from the use of alarger amount of the inhibitor. Moreover, the steel plates pickled inthe presence of the inhibitor set forth are clean and are not stainedupon removal from the bath.

Other phosphoric acid derivatives of the reaction products of sulfurdioxide and aldehyde-amine products, and preferably phosphoric acidderivatives of the reaction products of sulfur dioxide and aldehydederivatives of Schiifs bases have been prepared in a manner analogous tothat hereinbefore set forth and tested as inhibitors in a pickling bathin the manner described.

Thus, the phosphoric acid derivatives of the sulfur dioxide reactionproducts of a Schiffs base and of aldehyde derivatives thereof as setforth hereinafter, were prepared in a manner analogous to thathereinbefore set forth and the final product so obtained employed in apickling bath and tested in the manner described. The products referredto in the results set forth in Table I, as inhibitors A to G inclusive,represent the phosphoric acid derivatives of the sulfur dioxide reactionproduct of the following bases:

Oompozmd A.Anhydro formaldehyde aniline.

Compound B.-Reaction product of substantially three molecularproportions of butylaldehyde and substantially one molecular proportionof aniline.

Compound C.Reaction product of substantially three molecular proportionsof acetaldehyde and substantially two molecular proportions ofortho-toluidine.

Compound D.Reaction product of substantially one molecular proportion ofbetanaphthylamine and substantially one molecular proportion offormaldehyde.

Compound E.Reaction product of substantially one molecular proportion oforthotoluidine and substantially three molecular proportions ofbutylaldehyde.

Uompo'u/nd F .Reaction product of substantially one molecular proportionof 2,4- diamido diphenylamine and substantially three molecularproportions of heptaldehyde.

Compound G.-Reaction product of sub stantially one molecular proportionof aniline and substantially three molecular proportions ofheptaldehyde.

The following table shows the comparative loss in Weight when testpieces 3 x 4" of 30 gauge low carbon steel were pickled forty minutes in6% sulfuric acid at 80 C.

252. COMPOSITIONS,

in the presence of one of the preferred inhibitors and in the absence ofan inhibitor.

Table I W htl Weight Weight of Weight of mg Inhibiting comofinhibsteelstrip steel strip g pound employed itor embefore after gj g ployedpickling pickling exposed Grams Grams Grams Grams Compound A 0.06 18.562 18.098 0.0193 Compound B 0.06 18. 427 17. 629 O. 0333 Compound C 000 18. 032 17. 760 0. 0113 CompoundD 0. 06 17. 824 17. 700 0. 0052Compound E 0.06 18. 837 17.220 0. 0674 Compound F 0.06 18.144 17.9760.0070 Compound G 0.06 17. 951 17.823 0. 0053 None None. 17. 9% 10. 7630. 2985 It is thus apparent from the data set forth that the preferredclass of materials constitutes an important group of inhibitors, as inall the examples set forth wherein one of the preferred inhibitingcompounds was incorporated in the pickle liquor, there resulted a metalsaving of a large percentage of the loss in weight of the steel teststrips that results when no inhibitor was employed.

It has been found that other ratios of phosphoric acid, sulfur dioxideand aldehydeamine than those hereinbefore set forth may be reacted andemployed as inhibitors. Thus, substantially one molecular proportion ofthe aldehyde derivative of a Schitis base formed by reactingsubstantially three molecular proportions of acetaldehyde withsubstantially two molecular proportions of aniline has been reacted withsubstantially seven-tenths of a molecular proportion of sulfur dioxide,and the product so formed has been reacted with substantially twothirdsof a molecular proportion of phosphoric acid. The compound thus producedwas incorporated in a pickle liquor in the manner hereinbeforedescribed. The amount of inhibitor used and the size and grade of steelsheets used was the same as in the above described tests. A sheetweighing 18.246 grams was found after pickling forty minu es to havelost but 0.302 grams, or 0.0126 grams per square inch of surfaceexposed. A sheet of the same stock weighing 17 .928 grams and treated inthe same manner, but with no inhibitor present, suffered a loss of 7.165 grams total weight or 0.2985 grams per square inch of surfaceexposed.

Although it is desirable that the preferred inhibitor be prepared in thepresence of an organic solvent, as for example acetone, benzene and thelike, it is not imperative that a solvent be employed. The sulfurdioxide may be reacted with the aldehyde amine product withoutdissolving the latter in a solvent, and the product so formed may befurther reacted with phosphoric acid, forming a compound of thepreferred type, which possesses the inhibiting qualities desired.

Other modes of employing inhibitors of the type set forth herein in theacid pickling of metals are apparent to those skilled in the art towhich this invention pertains. The products described additionally maybe employed in the pickling process in the presence of foaming agents,ionizable substances or other materials ordinarily used, as well as thedifferent acids customarily employed in the pickling of various metals.

What is claimed is:

1. A process of pickling a metal which comprises subjecting the metal tobe pickled to the action of a substantially non-oxidizing mineral acidsolution containing a small proportion of a phosphoric acid derivativeof a reaction product of sulfur dioxide and an aldehydc aimne product.2. A proces o f pickling a metal which comprises subjecting the metal tobe pickled to the action of a substantially non-oxidizing acid solutioncontaining a small proportion of av phosphoric acid derivative of areaction product of sulfur dioxide and an aliphatic aldehyde-aromaticamine reaction product.

3. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a phosphoric acid derivativeof a reaction product of sulfur dioxide and an aldehydeaniine product.

4. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a. sulfuric acidsolution containing a small proportion of a phosphoric acid derivativeof a. reaction product of sulfur dioxide and an aliphaticaldehyde-aromatic amine reaction product.

5. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion Limil'flli jl of a phosphoricacid derivative of a reaction product of sulfur dioxide and an aldehydederivative of a SchitPs base.

6. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a phosphoric acid derivativeof a reaction product of sulfur dioxide and an aliphatic aldehydederivative of a Schiffs base.

7. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a phosphoric acid derivativeof a reaction product of sulfur dioxide and a material formed byreacting an aliphatic aldehyde containing less than eight carbon atomswith a. primary aromatic amine.

8. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a phosphoric acid derivativeof a reaction product of sulfur dioxide and a material formed byreacting substantially three molecular proportions of acetaldehyde withsubstantially two molecular proportions of aniline.

9. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a sulfuric acidsolution containing a small proportion of a product formed by reactingsubstantially one-half a molecular proportion of sulfur dioxide withsubstantially one molecular proportion of the reaction product ofsubstantially three molecular proportions of acetaldehyde andsubstantially two molecular proportions of aniline and further reactingthe product thus formed with substantially one molecular proportion ofphosphoric acid.

10. A process of pickling iron and steel products which comprisessubjecting the metal to be pickled to the action of a. sulfuric acidsolution containing a small proportion of a product formed by reactingin the presence of acetone substantially one-half a molecular proportionof sulfur dioxide with substantially one molecular proportion of thereaction product of substantially three molecular proportions ofacetaldehyde and substantially two molecular proportions of ani line andfurther reacting the material thus formed with substantially onemolecular proportion of substantially 85% phosphoric acid.

11. A pickling bath for metal products which comprises a substantiallynon-oxidizing mineral acid solution containing a small proportion of aphosphoric acid derivative of a reaction product of sulfur dioxide andan aldehyde-amine product.

12. A pickling bath for metal products which comprises a substantiallynon-oxidizing mineral acid solution containing a small proportion of aphosphoric acid derivative of a reaction product of sulfur dioxide andan aliphatic aldehyde-aromatic amine reaction product.

13. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a phosphoric acidderivative of a reaction product of sulfur dioxide and an aldehyde-amineproduct.

14. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a phosphor ic acidderivative of a reaction product of sulfur dioxide and an aliphaticaldehyde-aromatic amine reaction product.

15. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a phosphoric acidderivative of a reaction product of sulfur dioxide and an aldehydederivative of a Schifls base.

16. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a phosphoric acidderivative of a reaction product of sulfur dioxide and an aliphaticaldehyde derivative of a Schiifs base.

17. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a phosphoric acidderivative of a reaction product of sulfur dioxide and a material formedby reacting an aliphatic aldehyde containing less than eight carbonatoms with a primary amine.

18. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a phosphoric acidderivative of a reaction product of sulfur dioxide and a material formedby reacting substantially three molecular proportions of acetaldehydewith substantially two molecular proportions of aniline.

19. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a product formed byreacting substantially one-half a molecular proportion of sulfur dioxidewith substantially one molecular proportion of the reaction product ofsubstantially three molecular proportions of acetaldehyde andsubstantially two molecular proportions of aniline and further reactingthe material thus formed with substantially one molecular proportion ofphosphoric acid.

20. A pickling bath for iron and steel products comprising a sulfuricacid solution containing a small proportion of a product formed byreacting in the presence of acetone substantially one-half a molecularproportion of sulfur dioxide with substantially one molecular proportionof the reaction product of substantially three molecular proportions ofacetaldehyde and substantially two molecular proportions of aniline andfurther reacting the material thus formed with substantially onemolecular proportion of substantially 85% phosphoric acid.

In testimony whereof I hereunto aflix my signature.

DEAL H. TOMPKINS.

